RT Journal Article SR Electronic T1 The Value of Measuring Inspiratory Capacity in Subjects With Cystic Fibrosis JF Respiratory Care FD American Association for Respiratory Care SP 981 OP 987 DO 10.4187/respcare.05920 VO 63 IS 8 A1 Daphna Vilozni A1 Adi Dagan A1 Moran Lavie A1 Ifat Sarouk A1 Bat-El Bar-Aluma A1 Moshe Ashkenazi A1 Sarina Levy Mendelovich A1 Yael Betzalel A1 Ori Efrati YR 2018 UL http://rc.rcjournal.com/content/63/8/981.abstract AB BACKGROUND: Inspiratory capacity (IC) is often overlooked as an important measured index of spirometry in patients with cystic fibrosis (CF). Abnormally low IC may indicate the onset of static/dynamic hyperinflation, which may be accompanied by dyspnea and an increase in the work of breathing. This cross-sectional study sought to determine whether measuring IC during spirometry, may add clinical value to FEV1 measurements in CF subjects.METHODS: Anthropometric, clinical, spirometry, and static lung volume data were gathered retrospectively from 98 of 165 subjects with CF (mean ± SD age 26.8 ± 11.0 y) registered in The Edmond and Lily Safra Children's Hospital, Sheba Medical Centre, Israel. We compared the IC (% predicted) to FEV1, static lung volumes, and hospitalization days/year.RESULTS: IC decreased alongside FEV1 decline but at a slower pace (r2 = 0.32). Incremental trapped air, as measured by residual volume (RV), and a rapid elevation in the ratio of RV to total lung capacity occurred when IC deteriorated below 60% predicted values. The unique combination of IC < 50% predicted and FEV1 > 40% predicted induced an increase of up to 125 hospitalization days/year compared to subjects having IC > 50% predicted (up to 73 d/y, P < .001).CONCLUSIONS: Measuring IC in CF subjects may reveal silent worsening of lung function as indicated by a decline in IC < 50% predicted while FEV1 is still > 40% predicted. This condition may lead to inefficient breathing at high lung volumes, which may explain a subjective sensation of breathlessness and lead to an increase in hospitalization days/year.